The invention relates to methods of laying elongate articles in sub-sea applications, and in particular to methods of laying multiple articles such as pipes or cables in parallel, and strapping them together in the process.
The invention further relates to an apparatus for use in such methods, and, in particular, to an automated strapping system for continuously strapping at least two lines together.
As the offshore industry moves into deeper waters and marginal field developments, there is a constant drive to reduce costs through introduction of improved technology. These field oil development projects are using floating production units such as ships and semi-submersible rigs often combined with subsea tiebacks.
In subsea installations, flowlines, risers including service and injection lines connect subsea wells to the processing facilities. These pipes are configured in individual, xe2x80x9cpiggybackxe2x80x9d, umbilical or other modes. As the field developments move into deeper waters, the oil industry needs to develop products and systems accordingly. Spoolable composite pipes offer products with technical and economical potential in static and dynamic systems for deep-water subsea tiebacks. Especially promising are composites used in dynamic umbilicals and risers.
While piggyback installations are well known, for example where a methanol service line is laid simultaneously with a larger diameter oil or gas production line. In other applications, hydraulic and/or electrical service lines may be included in such a bundle. The invention may further be applicable to the laying of electrical and optical cables, as opposed to conduits for fluids such as oil, gas and water.
It is known in such applications to bind two conduits together using typically a series of steel bands, of the general type widely used in packaging heavy goods for transport. These bands have traditionally been applied by hand, using a special-purpose tensioning and fastening device. Such methods limit the speed at which the pipe bundle can be laid. Moreover, delicate articles including modem continuous composite pipes and coated pipes, can be damaged by the hard-edged steel banding.
The present invention in various aspects has the object of alleviating one or both of the above drawbacks in the prior art.
A first aspect of the invention comprises the use of a flexible adhesive tape to bind an elongate article or bundle of articles during sub-sea laying operations. Although the invention is intended primarily for binding two or more articles so as to keep them together and/or take the strain from or one or other of them, there may equally be applications, where a single article is being laid, for example, where the tape provides desirable properties as a coating for the article, or is used to bind a coating or sheath to the article.
The tape may for example comprise fibre reinforced plastic, for example glass fibre reinforced plastic tape. Such a tape is far less likely to damage delicate articles, being more compliant in shape than the convention steel bands.
The tape may be applied substantially continuously during laying, to form one or more helical windings. In a preferred embodiment, two helical tape windings are applied during laying, with opposite senses of rotation.
A second aspect of the invention provides an apparatus for laying elongate articles sub-sea, the apparatus including at least one carrier for a tape spool, arranged for the spool to rotate while moving bodily around the axis of the article during laying. Compared with conventional banding operations which have generally been performed at a horizontal section of pipe, embodiments of the invention provide an apparatus suitable for operation where the axis of the pipe or other article is vertical or substantially inclined, according to the desired angle of deployment beneath the sea surface.
The apparatus may in particular be mounted within a vertical or tiltable laying tower or xe2x80x9cstingerxe2x80x9d, downstream of equipment which supports the weight of the article during paying out. The apparatus is thus suitable for xe2x80x9cJ-Layxe2x80x9d operations in deep water.
The apparatus may have more than one rotary spool carrier, for example to achieve the double helix mentioned above. Each spool carrier may be arranged for powered movement around the axis, or for movement by hand. Guide means may be provided between the spool and the axis of the article, for impinging on a non-adhesive surface of the tape, so as to guide it onto the article being laid. The spools themselves need not be driven, the tape being drawn automatically from the spools by the rotation of the spool carrier and by the axial progress of the article during laying.
In a preferred embodiment disclosed herein, the apparatus includes adjustable guides above and/or below the location of tape winding, in order to keep a bundle of articles together in a desired configuration during binding.
In the preferred embodiments disclosed herein, the guide means and the rotary arrangement of the spool carrier about the axis of the pipe bundle or other article to be laid are made openable, so that the apparatus can be positioned for operation around the axis of an article without the need to thread the end of that article through the apparatus as an initial step. The apparatus may be mounted permanently in a laying tower or other laying arrangement, to be retracted when not in use, and to be deployed about the axis of the article being laid as required.